I have a desktop to which I remote in via rdp using my laptops, tablets etc., everything works fine here. (Username: MicrosoftAccount\myemail@outlook.com, password: mypass)

I want to give another user remote access to this desktop. So I added his email address (abc@outlook.com) via "Manage other accounts", enabled remote access for this email via "System Properties" --> "Remote" --> "Select Users"

Now, when he tries to login using his email, Username: MicrosoftAccount\abc@outlook.com, password: HisOutlookPassword, via RDP, he gets error "the credentials that were used to connect to MyDesktop did not work. Please enter new credentials."

Anything I am missing? Does he need to physically login to my desktop for the first time?